Solar activity and climate show correlations over a wide range of timescales. It is important to understand the behavior of the 27-day solar rotational period in lightning activities because it provides an opportunity to understand how the sun influences weather and climate. We analyzed lightning data extracted from diaries written in Kyoto, Japan from the mid-17th to the mid-18th century. Lightning shows the signal of the 27-day period; however, it disappeared during the Maunder Minimum.

Detailed analyses of the 27-day solar rotational period in cloud and lightning activities may help in untangling the process of solar influence on weather and climate. We analyzed the lightning data in Japan for AD 1989–2015 and found that the 27-day solar rotational period is seen in wide-area lightning activity. The signal was stronger at the maxima of solar decadal cycles. It was also found that the signal of the 27-day period migrates from the southwest to the northeast in Japan.

This paper presents an investigation into the sources of atmospheric gravity waves observed at 90 km above Amundsen-Scott South Pole Station, Antarctica. By combining gravity wave characteristics obtained from imager data and a numerical model for 3-D wave propagation through the atmosphere, we find that the development of baroclinic instabilities via displacement of the polar vortex is a significant and unique source of vertically propagating, short-period (< 1 h) gravity waves in the region.

A number of current systems exist in the Earth's magnetosphere. It is very difficult to identify local measurements as belonging to a specific current system. Therefore, there are different definitions of supposedly the same current, leading to unnecessary controversy. This study presents a robust collection of these definitions of current systems in geospace, particularly in the near-Earth nightside magnetosphere, as viewed from a variety of observational and computational analysis techniques.

Using a new air-shower simulation driven by the proton flux data obtained from GOES satellites, we show the possibility of significant enhancement of the effective dose rate of up to 4.5 µSv/hr at a conventional flight altitude of 12 km during the largest solar proton event that did not cause a ground-level enhancement. As a result, a new GOES-driven model is proposed to give an estimate of the contribution from the isotropic component of the radiation dose in the stratosphere.